The Pigmentary Effector System: a Review of the Physiology of Colour Response

Abstract

AMONG the many unsolved problems of animal life., the significance of pigmentary colour and of rapid colour-change is one of the most elusive and attractive. Unlike the case of chlorophyll, the pigments of animals have no direct physiological value so far as really critical evidence goes at present. The colouring matters of birds' eggs, for example, the variable colouring of the egg of the guillemot, herring-gull, or cuckoo, has not yet been shown to possess the slightest relation to the welfare of the chick; nor has the (genuine) coloration or lack of colour in the skin or deeper tissues been proved conclusively to play a definite part in the welfare of the animal body. On the other hand, adaptational and survival value has been freely admitted, until recently, to account for the complex and exquisitely balanced correlation between coloration, habit, and environment in a large number of instances, of which insects and fishes offer the most notable examples. The difficulty that has made biologists sceptical of arguments that are used to prove protective, warning, and epigamic significance in animal colouring, lies in the absence of objective standards of excellence. How much does it benefit a flat-fish to fit so exactly into its niche and to stay there? How much does the note of warning avail? What was the value of the rough study in pigment before the painted animal canvas became amenable to the criticism of life? Are pigments or structural colours anything more than indices of chemical and physical structure, and is their biological value real or apparent only? The Pigmentary Effector System: a Review of the Physiology of Colour Response. By Dr. Lancelot T. Hogben. (Biological Monographs and Manuals.) Pp. xi + 152. (Edinburgh and London: Oliver and Boyd, 1924.) 10s. 6d. net.